- When you add two numbers together you find how many you have in all.
- When zero is added to a second number the answer is the second number.
- Adding one is similar to counting up by one.
- Adding two is similar to counting up by two.
- Adding three is similar to counting up by three.
- To add two-digit numbers
Place one number above the other so the tens' place digits and ones' place digits are lined up.
Draw a line under the bottom number.
Add the two ones' place digits.
Add the numbers in the tens' place column
- Adding three numbers:
Mentally add the first two numbers.
Add the other number to this sum.
- To add three-digit numbers
Place one number above the other so the hundreds' place digits, the tens' place digits and ones' place digits are lined up. Draw a line under the bottom number.
Add the units digits
Add the tens digits
Add the hundreds digits
- Another way to estimate the sum of two numbers is to round each number and then add the rounded numbers. It is likely that this won't be the exact answer but it may be close enough for some purposes.
Round each term that will be added
Add the rounded numbers
Some uses of rounding are:
Checking to see if you have about enough money to buy what you want.
Getting a rough idea of the correct answer to a problem.
Directions: Find the sum of the following. Also write at least twenty examples of your own.